The present invention relates to a propeller propulsion unit for aircrafts in general.
Aircrafts in general that do not use jet propulsion systems are conventionally provided with one or more propellers that convert the power supplied by the motor into traction.
The propellers normally used are of various kinds, such as for example pusher or pulling propellers, with fixed or variable pitch, and ducted; these propellers are furthermore constituted by two or more blades that are arranged so as to balance, on the propeller axis, both the action of the centrifugal force, produced by the rotation of said propeller, and the moments caused by the aerodynamic forces generated by the relative speed of the blade with respect to the air.
Propellers having a single blade are used exclusively in the field of flying model aircrafts, i.e., with powerplants having extremely small power ratings.
The use of a single-blade propeller would certainly be useful in many applications in aircrafts, since it would be possible to improve the efficiency of the propeller and have considerable constructive simplicity; however, this type of use has so far been unfeasible, since all the problems that arise from compensating the radially-directed forces, inertial forces, and aerodynamic forces, with their corresponding moments, generated by the relative speed of the blade with respect to the air, have not been solved. These factors, which also vary as the relative speed of the blade with respect to the air varies, would produce troublesome stresses and vibrations that might lead to fatigue failure, especially if considerable masses are involved.
Accordingly, the use of a propulsion unit with single-blade propeller has never had a practical follow-up.